Rubber compositions



Patented Mar. 26, 1946 RUBBER COMPOSITIONS Arnold R. Davis, Riverside,Conn, assignor to American Cyanamid Company, New York, N. Y., acorporation of Maine No Drawing. Application May 8, 1943 Serial No.486,204

10 Claims.

This invention relates to accelerators for the vulcanization of rubberand sulfur-vulcanizable rubber-like materials. Mor particularly, theinvention is concerned with vulcanization accelerators obtained byreacting a diarylguanidine-acidic metal salt adduct with formaldehydeand a, substance selected from a group consisting ofmercaptobenzothiazole, benzothiazole disulfide and mercaptothiazoline.

The following, in which parts are given by weight, are illustrative ofsome of the methods of producing these vulcanization accelerators whichare more particularly described and claimed in my cO-pending applicationSer. No. 486,205, filed of even date.

COMPOUND A A mixture was prepared of the following materials:

Parts (DOTG) 2.ZnClz 614 Paraformaldehyde 180 Mercaptobenzothiazole 1002This mixture was heated together in a suitable vessel at 70-80 C. forabout 30 minutes until a yellow paste was formed. The temperatureof themass was raised to 90-100 C. and heating was continued at thattemperature for about 15 minutes at which time the paste began toconvert to a clear liquid. After several minutes additional heating atthis temperature the entire mass became clear. Upon cooling to roomtemperature the liquid solidified to a straw-colored resinous solidwhich had a softening point of about 70 C.

COMPOUND B A mixture was prepared containing the following materials:

(DOTG) 2.ZnC12 614 Paraformaldehyde 360 Mercaptobenzothiazole 2004tinuing the heating at about 100 C., the paste was converted to a clearliquid which solidified at room temperature to a clear resinous solid.

COMPOUND C A mixture was prepared of the following materials:

Parts Parts (DOTG) 2.ZnC12 1225 Paraformaldehyde Mercaptobenzothiazole334 This mixture was fused together by heating at about C. until asubstantially clear liquid was formed, which, on cooling to roomtemperature, became resinous. This resin softens at about 80 C.

COMPOUND D A mixture was prepared of the following ma- .terials:

Parts (DOTG) 2.ZI1C12 e; 614 Paraformaldehyde Z-Mercaptothiazoline 714Upon heating this mixture in a suitable container, a liquid was formedat about 60 C. Heating continued for about 1 hour at 75 C. and theproduct on being cooled to room temperature, was a substantially clearbalsam.

It should be noted that so far as the final product is concerned thereis no apparent distinction between first reacting the thiazolederivative with the aldehyde and then with the diaryl guanidineacid saltadduct "or whether the adduct, thiazole derivative and aldehyde arereacted simultaneously as in the preceding examples. Because it issimpler, th latter procedure illustrated in the foregoing examples issomewhat preferable. The method in which the adduct is reacted with apreviously formed aldehyde-thiazole reaction product is illustrated inthe following example.

COMPOUND E Methylol mercaptobenzothiazole was prepared in any suitablemanner such as by boiling a mixture of mercaptobenzothiazole with aslight excess over the molecular equivalent of aqueous formaldehydesolution, with or. without the addition of alcohol, the methylolmercaptdbenzo- COMPOUND F A mixture was prepared of the followingmaterials:

Parts (DPG) 2.ZnClz (diphenylguanidine zi n c chloride adduct) 1674Paraformaldehyde 540 Mercaptobenzothiazole 3006 This mixture was heatedfrom room temperature to 75 C. in about 20 minutes and at which time c dthe mass was partially melted. The temperature s was graduallyraisedreaching about 110 C. about 1 2 4O minutesjrfrom' theqstart of thereaction. A1; this point'themixture began to froth somewhat, watervapors being evolved. The reaction w s gffifiiftigitffiiiffiifififi:31;;3: I 28 $3 continued zit/110C. for an additional 30minutes. ""g t qw On cooling to room temperature, a cleargiresiniilzi%:i%% :::I 510 510 like material was obtained in a yield of 96.7% vbased on the starting materials. -"Trim-product" micgfifig fid B "i hada softening point of 70C. V

COMPOUND G- (lon poungg a r V mm. a A mixture was prepared with thefollowing ana inches) terials: v, .15 ,(DPGlzZnCla 1674 parts (1 mol) HI A U 1 2 i 'iar'aformald'ehyde V g 540 part's'-= (6 mols)iBenzOthiazoleflisulflde *2988'parts-(3*mo1s) 'i ?i: i*5??%o'sts' iii?Thismixture-wasfusedtogether,in.ta;suitable 20 Percent change +55 vesselby heating to about 125 C. and maintain- W 7 ing that temperaturelmtilzthe liquid product menslletest became clear and formed a clearfilm when flowed curedjatms I "out upon awitable-support. On cooling-toroom ,o. inmin. y 1 Qmpwndz temperature; the reaction product solidifiedtoa 5 r I r iblOWIliSh-OOIOIGd resin which had a softe i 21111; E long"Moder ,TenJ Elong, .PQlnt of aboutlO C. 1,496 I 75-0 1:400 32 COMPOUNDH if i 313%; e Qlji $1138 3.420 \,A-,soluti0n1oi45.5,parts zincch1oride=.,in-17:parts 7 ,watenrwasrmixedz'with140.7.partst-diphenylguanidiner anmthe mixture was r heated in -20n'1inutes Z 333333,ifgfigi it fi fiifiifif Mt n Q --Theetemperature-wasemaintainedat this point for about 18 minutes andringa further r m nneriodwof aboutt-20.v.minutes qthere '--WaS7;S1OW1y 5 i.addedaaemixturetof\.60,6 partsofr paraformalde- 3 4 5 7 .-rhyde1-=%,-excess)-1and 334.3 partsmercaptohenzo- V ;g

.thiazole;zheabing bein continuedcthmughoutvth gggagensi-agiggnecopolymer og 1 addi io Ata 1 m nutesfromthestart Carbonblack... 1 50 {50 L to auto -50 ,,the-:i-niti alreac-tionathetemperature-had-ereached gi ifgg -3 -3 1102.0. Thetemperature was-gradually increased *sr fiiurufjfnh I 10 I0...untilat-.100-;minutes.--from thetsta'rtnof the riniti-al ggg gggggleactiont-the,massshad -attained- .artemperatureof n -i 135 0., ,at,which point -it was held for an-raddi- 1 ti0nal-.30 minutes.:Thertotalztimeof reactionwas about'2 .-hours :10 minutes.

As in some of the previous examples, the prescmmmds ent reaction was"attended with some frothing, :wtheirothing and eyolutioniof watervapors;ceas- .-i g ,befpregtherendgof:the;(30eminuten'pe1tiodof r t jm b1-359JC; jojmcoofingxtofrooml tempera; Wilhamsfimm. .Yfiat1l00f0.,rmches ture, lear translucentdglassy:materialewes v d d pd;thisfproductwassfinflglassyfindz prac i%2;p1tSs0;Fs01e2jii;6- 0'5138-*0.'142 0.144 p. 138 0.140 v -ti fil ily free ficrysta-lsaafterstanding for 12 days. "-atss 0.;. 2.159 @155 154 ,.'159 'I fhi tspecifi'qygravitydof 1.4t1ral11dE a Percent change +152 +9.) +83-.5+11-.6- -+13.6 z-softening point f'66* C. r v v '"Thez-utilityiiofithe vulcanizationeacceleratorssof hatdnesgfwo'sem-"iwem Y thepresentfimzention;isiHustrated'byithe follow- 7 ing'rrlhber a-reclaimedrubber findt isyntheticrrub- "47 44 48 P46 '45 -ber-'likecrompoundscimwhich -partsL-are; given, by F54 --weight.' 'I'heeompositions-are compundeciin-the $3 12% "zusuaL-mannerabythe ;useof-rubber rolls. r l

Tensile tests jingle; Compound 3 Compound 47 Compound 5 mm Mod. "Ten.-'Elongl Mod! 'I3en.= ::Elon'g. sM'odJ' f'Tei1.-!: Elong. V

\ 710 355 M0 245 905 780 610 480 1, 290 ,620 1,005; 2, 470 7 5s0 -42o1,170 men 400 l;-8202 530 ==a9o 3:10 1,475 1,649 320' sauna-famo- 7: 50

Tensile tests Compounds Compound 6 Compound 7 Cure in min.

at 141 C. 12 13 14 Mod. Ten. Elong. Mod. Ten. Elong.

Butadiene-styrene copolymer 100 100 100 245 850 775 200 535 800Meroaptobenzothlazole 1. 5 975 2, e40 005 550 1, 600 075 Compound H 1.11.2 1, 770 2, 395 375 1, 250 2, 845 550 Coal tar softener 5 5 5 2,140 2,990 390 1, 640 3, 040 460 Easy processmg channel black 50 50 50 I Zmcoxide 5 5 5 1 Modulus (300%) and tensile in lb.lsq. in. 2 2 2 IElongation at break in percent.

Compounds Compounds (Williams 3 min.

Y at 100 0., inches) Natural rubber 50 50 Tire reclaim 85 85 Set-up orscorching tests-no heat 0. 163 0. 164 0. 165 Zinc oxide 3 3 After 1 hourboiling H O- 192 179 181 Sulfur 2.5 2.5 Percent change +18 +9 +10Snowflake whiting 22 22 After 1.5 hours in be 204 189 195 Clay 12 12Percent change +25 +15 +18 Medium process oil 2 2 Stearic acid 1 1 ICompound A 1.0 Shore hardness inch dwell Compound F 1.0 V

Minutes cured at 141 C.: Compounds (Williams 3 min. 25 Y" at 100 0.inches) 59 59 59 8 9 Tensile tests Set-uptestsno heat; 0.086 0.086 30After 1.5 hours, in 1120 at 85 C .238 .229 60 mmutes at 141 C. Per centchange +178 +166 Mod. Ten. -Elong. Tenszle tests 0 d Compound 12 575 2,885 545 0 8 ompoun s 9 Compound 13. 510 2, 900 585 ed at 141 Compound 14575 3, 040 565 C. 111 mm.

Mod. Ten. Elongfl Mod. Ten. Elong.

' After 48 hours at 100 C 20 860 2,105 515 790 2,080 520 30 875 2, 050495 8 5 2, 060 505 40 Compound 12 1,770 2, 200 230 40 820 1, 995 500 8152, 005 500 Compound 13 1, 505 2, 430 280 Compound 14 1, 570 2, 585 285 1Modulus (300%) and Tensile in lbJsq. in. Elmgamn at break percent 1Modulus 200%) and tensile in lb./sq. in.

I Elongation at break in percent. Com ounds p Rate of out growth wasdetermined on a De 10 n Mattia flexing machine with the standard groovedflexing sample. A cut .050 inch long Natural rubber 50 was 1n1t1al1 made1n the center of the groove The reclaim" s5 as half way between theedges of the test p1ece. ig 2 g 50 The test piece was then put in themachin and snowllaltewhiting 22. 5 22. bent thru an angle of 135 at therate of 375 ay 2 Medium process 011" 2 2 cycles per minute. The lengthof the cut as it Stearic aci 1 1 grew across the test piece was measuredafter fi ggi gggifg fii 6 the number of cycles given below. The lowerCompound G 0 figures indicate a lower rate of cut growth.

The average results are given below. Compounds (Williams 3 min.

Y at 100010" Inches) minutes cure at 141 C.

No. of cycles 10 n 60 Compound Compound Compound 12 13 14 is et-see terours in z a Per cent change $693351::::::::::::::::::::: 1%? fit it?20,000 -22 3 30,000 Tenszle tests ,000 J57 55 68 50,000 .82 .70 .83 0Compound 10 Compound 11 g g 1 After 24 hours at 100 C.

Mod. Ten. Elong. Mod. Ten. Elong.

1 Elongation at break in percent.

" accelerators have many a"dvaritages "over- Th above illustrationsindicatethatthe accelerators-of the present invention are very ef---fective in--the vulcanization of natural rubber compositions,compositions containing large -amounts ofreclaimed rubber andsulfur-vulcanizable synthetic rubber-like materials. =-From thedescribed results -obtained with compounds 12, 13, and'le; it "is'clearly'evi'dent that" hese captoberiz'othiaiole 'in "syntheticrubb'erOf 'thB butadiene-styrene copolymer type. It can be seen that-less ofmyaccelerator is-requiredto give 7 the same degree ofcure and with lesstendency toward "scorching. At optimum cure, higher"lofigatfiihsafidftefisile strengths are obtained with my accelerators;even after aging at 100 C.

" for "48 "'noursl rurmenrgcre, after agin the "cured compounds at 10c cror ne heufrs, :tnose containing my accelerator showed significantlylower rate of cut growth. 7

" The-rubber or rubber-like compositions produced, with the acceleratorsof the present invention are suitable for use in the production oftires, mechanical rubbengoods, heels, soles and the-like in accordancewith the usual practice" The rubberaccelerators prepared as described.

above or by equivalent-procedures appear to be chemical compounds ofcomplex molecular structure, having softening points which vary fromabout"6Q Q. to'less than 80 C. These products are chemically differentfrom fusion mixtures of v the diarylg'uani'dine-zinc chloride adductsand mercaptobenz othiaz ole which are opaque yellowcoloredsolids andwhich; when examined under the microscopefl-clearly show the glassyphasebf -thediarylg-uanidine-zinc chloride adducts and the tions'for;producingthe desired complexes may be varied -':quite considerablywithout substantially -air'ecti-ng th'e properties-of the products-obtained. 'St'arti-ng'withthe'same ingredients, there will besproducedin-general, the same chemical complex. Bysuitable methods oi-preparation,"

the endproductsmay be-made as resins or-may be obtained as crystallinecompounds. *Some of the resinousproducts:havea tendency to formcrystals=on standingat room temperature for extended periods oftime-Crystalline materials may -may be obtained which possess opticalroperties different from those of the starting materials,therebyindicating chemical reaction.

, The diarylguanidine-Zinc chloride adducts which are used for thepreparation of my new accelerators, may be made in any suitable manneras set forth in the-examples or in accordance with the disclosures 'ofmypatents, Nos. 2,259,063,

J 2,259,064gand 2,259.414, all issued October 14,1941.

" In placeof the zinc chloride referred'to, other anon 1 09 scribed inmy patents referred to above. The

-acidicsalts-oforganie acidsmay-also-be-used iee.,

- sulfate; stannous chloride, =stannic chloride, stan- .iious sulfateand s'tannic' sulfate. Othersuitable 'cliarylgu'anidines'may be-used,-'-e'. -g., 'phenylorthotolylguanidine. V a Other changes andvariationsmay' made in -carI-y-i-ng outthe presentlnventionwithout-departingfrom the spirit and scope thereof as de- -fined-in-theappended claims.

I claim: l.--'I-he--process which comprises vulcanizing rubber andsulfur-vulcanizable rubber-likema- "teria'ls in the resence of sulfurand aim cani'zationaccelerator comprising the stable'ch'emical cOmpieXSOftening at from about"65- 80-' Gibbtained by fusing one mol part of'adiarylguanidine-zinc chloride-adductwith one to twelve-m 1 parts ofparaformaldehyde and from' one'to-fl mol parts of a substance selected--from-thegroup consisting 0f mercaptobenzothiazole, benzothiazoledisulfi'de and m'ercaptothiazoline.

--2.""Ihe: process -which comprises vulcanizing rubber andsulfur-vulcanizable rubber-like materials in-the presence of-sulfurandavulcanization accelerator-comprising the stable chemical com- I plexsoftening at from about-80" C. obtainedby fusing one mol part of anadduct of diarylguanidine and an acidicsalt'of wmetal of the group-c0nsisting-of -zinc,--a l-uminum,-cadmiuin-and-tin, with about-one' to'tvvelvemolpartsof paraformaldehyde and --a-bout oneto twelve rnolpartsbf *a substance selected from the: group'monsisting ofmercaptebenzothiazole, ben'Zothi-azole -di-su-lfide andmercapt'othiazoline.

3. The process which comprises 'vulcanizing rubber andsulfur-vulcanizable rubber-like materials in the resence of sulfur-and'avulcanization accelerator comprising thech'emicalcomplex 'bbtamed byfusing from one to twelvemol parts of 'methyl'ol mercaptobenzothiazolewith about one mol part of diarylguanidine-zinc chloride adduct.

4. A vulcanizable composition comprising sulfur, andunvulcanizedmaterial selected from the group consisting of rubber andsenor-vulcanizable rubber-like materials, and-a vulcanization'accelerator comprising the' stable chemicalcomplex softening at fromabout 65-80" C. obtained" by fusing one mol part of a diarymaamdine zincchloride *adduct with about one to twelve mol parts of paraformaldehydeand about one to' twelve mol parts of a substance selected from thegroupconsisting of mercaptobenzothiazole, benzothiazole 'disulfide' andinercaptothiazoline 5. A vulcanizable composition comprising sulfur anunvulcanized material selected from the groupconsisting of rubber andsulfur-vulcaniza- -ble rubber-like materials, and a vulcanization=ac-'celerator comprising the" 'stablecherfiical 66m- "pleX softening atimmanent 65 80 C. "b"5taifid by fusing one mol part-of an adductcrammguanidine and an acidic salt of a metal of the group consisting ofzinc, aluminumficadmium and tin, with about one to twelve molpartsofparaformaldehyde and about'one to twelvemol parts of a substanceselectedfromthegroup consisting of mercaptobenzothiazole; ben'zothiazoledisulfide and m'ercaptothiaz'oline.

6. A'vulcanizable' composition comprisingsul- "fur; an unvuicanized'natena seie'cted' rrom the group consisting of rubbersand sulfur-vulcanizable rubber-like materials, and a vulcanization acceleratorcomprising the stable chemical complex softening at from about 65-80 C.obtained by fusing from one to twelve mol parts of methylol.

mercapto-benzothiazole with about one mol part of a diarylguanidine-zincchloride adduct.

'7. A composition comprising a material selected from the groupconsisting of rubber and sulfurvulcanizable rubber-like materials,vulcanized in the presence of sulfur and a vulcanization acceleratorcomprising the stable chemical complex softening at from about 65-80 C.obtained by fusing one mol part of a diarylguanidine-zinc chlorideadduct with about one to twelve mol parts of para formaldehyde and aboutone to twelve mol parts of a substance selected from the groupconsisting of mercaptobenzothiazole, benzothiazole disulflde andmercaptothiazoline.

8. A composition comprising a material selected from the groupconsisting of rubber and sulfurvulcanizable rubber-like materials,vulcanized in the presence of sulfur and a vulcanization acceleratorcomprising the stable chemical complex softening at from about 65-80 C.obtained by fusing one mol part of an adduct of diarylguanidine and anacidic salt of a metal of the group consisting of zinc, aluminum,cadmium and tin, with about one to twelve mol parts of paraformaldehydeand about one to twelve mol parts of a substance selected from the groupconsisting of mercaptobenzothiazole, benzothiazole disulfide andmercaptothiazoline.

9. A composition comprising a material selected from the groupconsisting of rubber and sulfurvulcanizable rubber-like materials,vulcanized in the presence of sulfur and a vulcanization acceleratorcomprising the stable chemical complex softening at from about 65-80 0.obtained by fusing from one to twelve mol parts of methylolmercaptobenzothiazole with about one mol part of a diarylguanidine-zincchloride adduct.

10. The composition of claim 4 in which the accelerator is prepared byfusing 1 mol of the adduct with 6 mols paraformaldehyde and 6 molsmercaptobenzothiazole.

ARNOLD R. DAVIS.

Certificate of Correction Patent N 0. 2,397 ,409. March 26, 1946. ARNQLDR. DAVIS It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows: Page 3, second column, line 71, in the table, second columnthereof, under the heading Compound 12 for .20 read .25 and that thesaid Letters Patent should be read with this correction therein that thesame may conform to the record of the case in the Patent Oflice.

Signed and sealed this 16th day of September, A. D. 1947.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

